Geneva was cold and gray when air force one touched down in November 1985. President Ronald Reagan had come to meet Mikhail Gorbachev, the newly appointed leader of the Soviet Union. Reagan was convinced that the risk of catastrophic nuclear war was high, and he wanted to reduce the two superpowers’ swollen arsenals. Gorbachev also recognized that the arms race was strangling the Soviet economy.

Yet the tête-à-tête quickly degenerated. Reagan lectured Gorbachev on the history of Soviet aggression. Gorbachev attacked Reagan’s Strategic Defense Initiative, an ambitious plan to knock incoming nuclear weapons out of the sky. Negotiations nearly broke down. At five in the morning, the two sides agreed to a joint statement with no firm commitments. At the bottom—almost as a footnote—Reagan and Gorbachev inserted a gauzy pledge to develop a new source of energy “for the benefit of all mankind.”